1. Field of the Invention
The present invention relates generally to NAS (network attached storage) load (work load) balancing systems, and more particularly to a technique for constructing a NAS system capable of sharing loads between composing nodes and thereby improving operability and performance by automatically routing a request issued from a NAS client to an appropriate node, considering the file access locality of the NAS client, in a NAS unit composed of multiple nodes such as computers and designed so that the same file can be accessed from any node.
2. Description of the Related Art
FIG. 1 is a schematic diagram illustrating a conventional NAS system in which a conventional NAS unit 1000 and a NAS client group are connected via a network 110 such as an IP network. Referring to FIG. 1, the NAS system includes the NAS unit 1000, the network 110, and computers 111, 112, and 113 forming the NAS client group.
The NAS unit 1000 includes a storage unit 104, multiple nodes 1010, 1020, and 1030, and a dispatcher unit 105. The dispatcher unit 105 is known as a method of distributing loads among the nodes 1010, 1020, and 1030.
According to this method, one logical IP address (LIP1) is defined for the NAS unit 1000, and each of the computers (NAS clients) 111, 112, and 113 issues a file operation request to this logical IP address. As described above, the dedicated computer called “dispatcher unit 105,” which is a special apparatus managing IP address conversion, is provided in the NAS unit 1000. The dispatcher unit 105 converts the logical IP address, which is the destination of the request issued by the NAS client 111, 112, or 113, into a unique physical IP address (MAC1, MAC2, or MAC3) determined node by node in the NAS unit 1000. As a result, the dispatcher unit 105 routes the request to the destination node.
This conventional method can provide access that can make the internal node configuration of the NAS unit 1000 transparent to the NAS clients 111 through 113, but increases the cost of the NAS unit 1000. Further, there is a disadvantage in performance in that overhead accompanying IP address conversion affects the throughput of the NAS unit 1000. For instance, there is a problem in that if the requests from the NAS clients 111 through 113 reach the NAS unit 1000 at such a frequency as to exceed the processing capacity of the dispatcher unit 105, the throughput of the NAS unit 1000 cannot be increased with scalability no matter how many nodes the NAS unit 1000 has.
FIG. 2 is a schematic diagram illustrating a conventional NAS system where the conventional NAS unit 1000 and the NAS client group are connected via the network 110 without employment of the dispatcher unit 105 of FIG. 1. In FIG. 2, the same elements as those of FIG. 1 are referred to by the same numerals.
Referring to FIG. 2, the NAS unit 1000 includes the multiple nodes 1010, 1020, and 1030 and the storage unit 104. The nodes 1010, 1020, and 1030 have their own IP addresses (IP1, IP2, and IP3, respectively). When the computers 111 through 113 forming the NAS client group access the NAS unit 1000, each of the NAS clients (computers) 111 through 113 uses any fixed one of the IP addresses (IP1, IP2, and IP3) assigned to the nodes 1010 through 103 so as to always access the storage unit 104 in the NAS unit 1000 via the same single node. For instance, the NAS client 111 always accesses the storage unit 104 via the node 1010, the NAS client 112 always accesses the storage unit 104 via the node 1020, and the NAS client 113 always accesses the storage unit 104 via the node 1030.
However, there is a problem in that when each of the NAS clients 111 through 113 always accesses the storage unit 104 via the same node in the NAS unit 1000, loads cannot be balanced among the nodes 1010, 1020, and 1030.